Search

Pre-synchronization has been evaluated as a method to improve synchrony of ovulatory follicles before fixed-time AI (FTAI). The objective was to compare FTAI results in beef cows from two protocols that utilize pre-synchronization. Blood samples were collected on d-14 (d0=CIDR removal) to determine progesterone concentration at the start of synchronization (P4start: ≥1ng/mL=high, < 1ng/mL=low). In a subset (n=1,032), an additional blood sample was taken between d-21 and -29 to determine cyclicity. Cows (n=1,119), from 21 herds, were grouped by days postpartum and age and randomly assigned to one of two protocols. Cows assigned to the PG 6-day CIDR protocol (PG6d) received prostaglandin F2α (PG) on d-9, CIDR insertion and GnRH on d-6, and CIDR removal and PG on d0. Cows assigned to the 7&7 Synch protocol (7&7) were administered PG and CIDR insertion on d-14, GnRH on d-7, CIDR removal and PG on d0. For both protocols, FTAI occurred coincident with GnRH 66 h after second PG. Pregnancy was determined by transrectal ultrasonography 30-40 d following FTAI. The GLIMMIX procedure of SAS (9.4) was used to detect differences in estrus response and pregnancy success with herd included as a random variable. Estrus response (0 to 66 h) was influenced by treatment (P< 0.01; PG6d=60±5% and 7&7=74±4%), Body Condition Score (P< 0.01), cycling status (P=0.03), P4start (P< 0.01), and a P4start by treatment interaction (P< 0.001; PG6d-highP4=62±6%, PG6d-lowP4=58±6%, 7&7-highP4=84±3%, 7&7-lowP4=60±6%). Pregnancy success was influenced by estrus expression (P< 0.01; estrus=38±4% and no estrus=62±6%), and a treatment by P4start interaction (P=0.04; PG6d-highP4=58±5%, PG6d-lowP4=39±7%, 7&7-highP4=49±5%, 7&7-lowP4=55±8%) but was not influenced by treatment (P=0.45; PG6d=49±4% and 7&7=52±4%). In conclusion, effectiveness of pre-synchronization method depends on a cows’ physiological status at the beginning of the protocol. The 7&7 protocol increased estrus response compared to PG6d, but there was no difference in pregnancy success.

It has been reported that plasma serine protease inhibitor (SERPINA5) and dystroglycan (DAG1) are loosely attached to the sperm and SERPINA5 can also be present on sperm tails. The objective of this study was to evaluate whether SERPINA5 and/or DAG1 could be used as a fertility marker in dairy bulls. Frozen semen from dairy bulls (n=19) were evaluated for concentration of SERPINA5 and DAG1 and percentage of sperm tail labeled for SERPINA5 (SERPINA5-tail) by immunofluorescence in a minimum of 200 sperm cells per bull in two different ejaculates. Semen was evaluated for total motility, progressive motility, and viability. Semen was used for in vitro embryo production (~150 oocytes/bull). Bull fertility was classified by two methods, sire conception rates [SCR - High-SCR ( >1.0) or Low-SCR (< -4.0)] and the ratio of embryos that developed into a blastocyst (BL) from those that had cleaved (CL) as Good (BL/CL≥38.5%) or Poor (BL/CL< 38.5%). The GLIMMIX procedure of SAS was used to evaluate fertility classification with SCR, BL/CL, and the interaction in the model with bull as a random effect. Progressive motility, CL, SERPINA5 and DAG1 concentration, and SERPINA5-tail did not differ (P≥0.14) among SCR and BL/CL classifications or their interaction. There was no difference (P>0.33) in total motility between High-SCR and Low-SCR or BL/CL classification; however, the interaction was significant (P=0.02; High-SCR/Good 54.9±2.8%, High-SCR/Poor 39.4±5.4%, Low-SCR/Good 44.8±4.5%, Low-SCR/Poor 52.03±3.2%). High-SCR bulls had decreased BL (P=0.03; 30.6±1.6%, 35.8±1.4%, respectively) and tended to have decreased BL/CL ratio (P=0.10; 38.1±2.0%, 42.9±1.8%, respectively) compared with Low-SCR bulls. In summary, DAG1 and SERPINA5 do not seem to be a putative fertility marker. In vitro embryo production is not a good predictor of SCR, since High-SCR and Low-SCR bulls may have Good or Poor in vitro embryo developments.

Damage to the bovine corpus luteum (CL) has been reported following modified-live virus vaccination (MLV). The objective of this study was to investigate the degree of luteal apoptosis after MLV or inactivated vaccine (IV) administration at time of artificial insemination. Beef females were estrous synchronized and on d 0 were vaccinated with a MLV or IV after being transrectally ultrasounded to record presence and location of dominant follicles and CL. Thirteen cows (MLV, n=7; IV, n=6) were selected on d 10-13 across treatment based on dominant follicle size and estrus expression for ovariectomy. Ovaries were obtained and CL were frozen in OCT and sectioned for immunohistochemistry analysis. At the time of ovary collection, some MLV animals had two CL. These were characterized into old or new CL, relative to if ovulation had occurred in response to the synchronization protocol or afterward due to an abnormal cycle, respectively. For immunohistochemistry analysis, two nonconsecutive sections were evaluated for apoptosis using a TUNEL staining kit (ab66110) according to manufacturer’s instructions, with the modification of DAPI being used as a cell marker. Two random fields of view from each section were photographed with a Keyence BZ-X810 microscope and were evaluated for number of total and apoptotic cells. The GLIMMIX procedure of SAS was utilized to analyze percentage of apoptotic cells with image included as a random effect. Percentage of apoptotic cells were affected by treatment (P < 0.0001). MLV-new CL had the greatest percentage (35.56 ± 5.5%) of luteal cell apoptosis, while MLV-old CL (7.05 ± 4.6%) and IV (4.24 ± 4.9%) were similarly decreased. In summary, a greater degree of apoptosis in new CL which formed after an abnormal cycle following MLV administration indicates the ability of MLV to induce estrous cycle dysfunction and extend its effects to luteal cell development and function.

The objective of this study was to determine factors impacting abundance of pregnancy-associated glycoproteins (PAGs) after embryo transfer. Cows were synchronized using the 7-d CO-Synch+CIDR® protocol and grouped by estrus expression 48h after prostaglandin (d0) [Estrual (PC): n = 198; Non-estrual: n = 406]. Non-estrual cows were administered GnRH and randomly assigned to Estradiol treatment (E2: n=202; 0.1mg estradiol 17-β) or no treatment (NC: n = 204). In vivo produced embryos were transferred on d7, with grade, stage, and flush balanced across treatments. Circulating concentrations of estradiol and progesterone were determined on d0 and d7, respectively. Abundance of PAGs was determined on d24 and d26. Cows that were pregnant on d30 were grouped by age (H: 2, C: >2 years) and subjected to analysis. Correlations were analyzed using PROC CORR in SAS, while PAGs were analyzed using PROC GLIMMIX with treatment, age, year, sire, and embryo grade and stage as fixed effects. Abundance of PAGs on d24 was influenced by treatment (P = 0.01; PC=0.75±0.09, E2=0.59±0.09, NC=0.56±0.08), age (P < 0.01; H=0.75±0.09, C=0.52±0.08), year (P < 0.0001; 2019=0.42±0.08, 2020=0.84±0.09), and sire (P = 0.02; A=0.49±0.12, B=0.62±0.09, C=0.47±0.11, D=0.77±0.08, E=0.83±0.21), but not embryo grade (P = 0.89) or stage (P = 0.40). There was a negative correlation between d0 estradiol and d24 PAGs (P < 0.0001, r=-0.34), and a positive correlation between d7 progesterone and d24 PAGs (P < 0.0001, r=0.36). On d26, PAGs tended to differ by treatment (P = 0.09; PC=2.43±0.20, E2=2.33±0.21, NC=2.03±0.20). Age (P = 0.02; H=2.48±0.22, C=2.05±0.16), and sire (P = 0.0007; B=2.01±0.20, D=2.52±0.17) influenced PAGs, but embryo grade (P = 0.33) and stage (P = 0.32) did not on d26. Sire was associated with PAGs, and presumably embryo attachment, but not pregnancy rate. Increased progesterone concentrations on d7 were correlated with earlier attachment as measured by PAGs. Estrus expression prior to d0 may enhance earlier attachment of the fetal/maternal interface, and supplemental estradiol on d0 may improve attachment by d26 when ovulation is induced. Funded by NIFA 2019-67015-29411.